As a method for molding a thin-walled packaging container formed from a synthetic resin, a technology is known, for example, which comprises positioning within a blow mold a preform obtained by injection molding or extrusion, and expanding the preform in a longitudinal direction and a lateral direction, to obtain a final container by biaxial stretch blow molding (see, for example, Patent Documents 1 to 3).
In the process of biaxial stretch blow molding, the preform is stretched using high pressure blowing air, and the stretched preform is pressed against the cavity face of the blow mold composed of a pair of split molds. By this procedure, the final container of a shape corresponding to the shape of the cavity face of the blow mold is obtained. Thus, the blow mold comprising the pair of split molds needs to maintain a reliable mold clamping state.
With a conventionally known biaxial stretch blow molding device, when each split mold is clamped, a force opposing the blowing pressure is exerted on the end face (parting face) on the cavity face side. That is, the pair of split molds is clamped by mold clamping mechanisms such as hydraulic actuators or toggles to exert a high clamping pressure on the parting faces.
In the case of the blow mold having the pair of split molds, the mold clamping state can be maintained reliably by exerting a high clamping pressure on the parting faces as mentioned above. Moreover, the opening and closing movements of the split mold are managed with high accuracy, whereby the mold clamping state of the pair of split molds can be maintained reliably, and the clamping pressure on the parting faces can be kept high. Patent Document 2 discloses a blow molding device having a guide member provided laterally of a blow mold so that the upward movement of the split mold can be regulated, with the motion of the split mold in the opening/closing direction being permitted, by the guide member. Patent Document 3 discloses a molding apparatus having a mold opening prevention mechanism provided laterally of a blow mold.